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Thu, 04 Jun 2020 22:27:29 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 054MRMoH033116; Thu, 4 Jun 2020 22:27:29 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userp3030.oracle.com with ESMTP id 31f92rs5ck-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 04 Jun 2020 22:27:28 +0000 Received: from abhmp0017.oracle.com (abhmp0017.oracle.com [141.146.116.23]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 054MRRwx023147; Thu, 4 Jun 2020 22:27:27 GMT Received: from ca-dmjordan1.us.oracle.com (/10.211.9.48) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 04 Jun 2020 15:27:27 -0700 Date: Thu, 4 Jun 2020 18:27:52 -0400 From: Daniel Jordan To: Dave Hansen Cc: Daniel Jordan , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , Dave Hansen , Michal Hocko , Pavel Tatashin , Peter Zijlstra , Steven Sistare Subject: Re: [PATCH] x86/mm: use max memory block size with unaligned memory end Message-ID: <20200604222752.ubwykq4himsjdult@ca-dmjordan1.us.oracle.com> References: <20200604035443.3267046-1-daniel.m.jordan@oracle.com> <5827baaf-0eb5-bcea-5d98-727485683512@redhat.com> <20200604172213.f5lufktpqvqjkv4u@ca-dmjordan1.us.oracle.com> <20200604181201.lqop72ihg5butlmz@ca-dmjordan1.us.oracle.com> <72066bef-866a-c2a4-d536-4212c3344045@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <72066bef-866a-c2a4-d536-4212c3344045@intel.com> User-Agent: NeoMutt/20180716 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9642 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 bulkscore=0 mlxscore=0 malwarescore=0 spamscore=0 suspectscore=0 mlxlogscore=978 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006040156 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9642 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 bulkscore=0 clxscore=1011 cotscore=-2147483648 malwarescore=0 adultscore=0 priorityscore=1501 suspectscore=0 phishscore=0 spamscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006040155 X-Rspamd-Queue-Id: E296A181070C0 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jun 04, 2020 at 01:00:55PM -0700, Dave Hansen wrote: > On 6/4/20 11:12 AM, Daniel Jordan wrote: > >> E.g., on powerpc that's 16MB so they have *a lot* of memory blocks. > >> That's why that's not papering over the problem. Increasing the memory > >> block size isn't always the answer. > > Ok. If you don't mind, what's the purpose of hotplugging at that granularity? > > I'm simply curious. > > FWIW, the 128MB on x86 came from the original sparsemem/hotplug > implementation. It was the size of the smallest DIMM that my server > system at the time would take. ppc64's huge page size was and is 16MB > and that's also the granularity with which hypervisors did hot-add way > back then. I'm not actually sure what they do now. Interesting, that tells me a lot more than the "matt - 128 is convenient right now" comment that has always weirdly stuck out at me. > I actually can't think of anything that's *keeping* it at 128MB on x86 > though. We don't, for instance, require a whole section to be > pfn_valid(). Hm, something to look into.